1. Field of the Invention
The present invention relates to a device which is used in an image forming apparatus such as an electrostatic process copying machine, laser printer, or facsimile machine to remove the electrostatic charge on a photoconductor.
2. Description of the Prior Art
In a conventional image forming apparatus of one kind, an electrostatic charge-removing device is installed ahead of the developing device as viewed in the movement direction of the photoconductor to remove the electrostatic charge in a desired region on the photoconductor before the development process. As an example, where a margin is formed around the front end of the paper to prevent it from being wound around the photoconductor, the electrostatic charge on that portion of the photoconductor which corresponds to this front end portion is removed. Where a document is copied excluding its one part or a part of a document is copied, i.e., so-called edited development is performed, the electrostatic charge in the desired portion on the photoconductor is removed. Also, electrostatic charge is removed from the unwanted image region that is placed outside the receiver paper, for preventing consumption of excessive toner.
The electrostatic charge-removing device is normally composed of light-emitting diodes regularly spaced from each other in a orthogonal direction to the movement direction of the photoconductor in a case. One example of such an array of light-emitting diodes (LEDs) is shown in FIG. 7, and each LED produces diffuse light. The diffuse light emitting from each LED draws a substantially square form on the surface S of the photoconductor. The characteristics of the brightness are such that it is highest in the center of the light and decreases toward the around area of the light. The distance by which the neighboring LEDs are spaced from each other is so determined that the successive diffuse light radiations emitted from the neighboring LEDs overlap partially with each other.
The case has light width-limiting portions 8a extending along the photoconductor 1, to define the width of the cross section of the diffuse light that is emitted from the LEDs 9 toward the photoconductor surface S. Therefore, the electrostatic charge on the surface S is removed within this width. However, in the locations d where the successive diffuse light radiations emitted from the neighboring LEDs 9 overlap with each other, the brightness is too intense and the light will reach the image area beyond the width defined by the width-limiting portions 8a. As a result, the light erases some of the necessary electrostatic charge, thus producing notches e in the final print. That is, the boundary between the image area and the non-image area is uneven slightly. Consequently, a part of the required image is lost.